Geological History of New Zealand - revision exercises.

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Question 1. Sedimentary rocks and their environment
a. Match the type of sedimentary rock with the depositional environment/mechanism
Key list: limestone, siltstone, coal, greywacke sandstone, loess, till, conglomerate

Sedimentary environment	main rock type from this environment
i Quiet river meanders and estuaries
ii. Wind blown dust, rock flour from glaciers
iii. Sediment often found near severe relief (mountains)
iv. Swampy forest or peat swamp
v. Biologically rich but sediment poor shallow sea
vi. Ground up material from glacier deposited in lake
vii. Submarine current on continental shelf/slope

b. Which of the rock types would you expect to have been laid down
(i) towards the most actve part of an orogeny?
(ii) during a period of marine transgression?
(iii) during an Ice Age?

c. Coal is often interbedded with siltstone. Explain why.

d. Explain why a suite of limestone and lime-rich sediment such as marl is evidence for a reduction in land area.

Question Two: Geological observations and interpretations
During different periods of geological history, certain processes dominate. For example, 120-130 million years ago the dominant processes were those typical of an orogenic phase.
Below is a list of some of the observations a geologist might make about particular rock strata. Write them into the appropriate column on the table.

Orogenic phase	Erosional/depositional phase	Marine transgressive phase

a. extensive coal deposits
b. regional unconformity
c. extensive greywacke sandstones
d. intrusions/contact metamorphism
e. limestones and marls
f. regional metamorphism
g. island arc volcanic rocks incorporated into sediment
h. conglomerates and breccias

Question 3: Peneplanation
Inland from Dunedin, the Taiere River cuts through schist which is metamorphosed material from the Rangitata Depositional Period. The landscape features around the river suggest the area contains remnants of the post-Rangitata peneplain.
a. Identify the area in the photo below which shows landscape features indicating peneplanation and explain how these landscape features were formed.

b. Explain why the sediments of the Rangitata Deposition Period in this area now form the rock type schist.
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